Optimization of 3-butenoic acid-modified polyalkenoic acid for enhanced glass ionomer cement performance

Glass ionomer cements (GICs) suffer from mechanical limitations due to rigid intermolecular hydrogen bonding in polyalkenoic acid (PCA) that impedes ionic cross-linking during setting. This study examined how molecular weight and solution concentration of modified polyalkenoic acid (PCA) containing 3-butenoic acid (VA) spacers at 8 mol% concentration (PCA-VA-8) influence comprehensive GIC performance.

PCA-VA-8 polymers with varying molecular weights (5.49 × 10⁴ to 15.57 × 10⁴) were synthesized via free radical copolymerization of acrylic acid, itaconic acid, and 3-butenoic acid by controlling initiator dosage. Experimental GICs were prepared using different PCA-VA-8 concentrations (40-60 wt%) and powder-to-liquid ratios (3.2:1 to 4.0:1). Mechanical properties were evaluated according to ISO 9917-1:2007 standards, while water sorption, solubility, aging resistance, and fluoride release were assessed over 4-week immersion periods.

The optimal formulation (molecular weight ≈8 × 10⁴, 50 wt% concentration, 3.6:1 powder-to-liquid ratio) achieved enhanced mechanical properties: flexural strength 54.14 ± 5.29 MPa, flexural modulus 19.00 ± 1.06 GPa, and compressive strength 221.35 ± 17.06 MPa (p < 0.05). This formulation showed 33 %-63 % higher flexural strength than commercial Fuji IX-GIC throughout 4-week water aging while maintaining excellent dimensional stability. Water sorption was reduced by 18 %-22 % during initial weeks compared to commercial materials, with solubility remaining comparable to controls (p > 0.05). Fluoride release analysis revealed an initial burst release of 4.1 μg/mL on day 1, followed by stabilization at 0.6-0.9 μg/mL from day 4 onward. Although lower than the initial release of commercial Fuji IX-GIC (6.2 μg/mL), the sustained fluoride levels remained above the therapeutic threshold necessary for remineralization and caries prevention.

VA-modified PCA enhances GIC mechanical properties through improved polymer chain flexibility while maintaining clinical requirements for water resistance and fluoride release, representing a promising advancement for next-generation restorative applications.